The present invention relates to a convection cooler, and in particular, one for cooling a gas produced in a gasification reactor under elevated pressure.
Such a convection cooler is known from the German patent No. 32 08 421. In this convection cooler a part of the bundle heating surfaces, which are arranged within the insert, are suspended from the removable lid of the container and can be pulled out of the insert. The further bundle heating surfaces provided in the lower part of the insert are connected to the insert. Water-cooled soot blowers, which are fixedly attached to the bundle heating surfaces, are used for cleaning the removable bundle heating surfaces. This arrangement, as such, is effective, but can be improved in some respects.
From U.S. Pat. No. 2,940,430 a coal combustion boiler is known, which has a primary combustion chamber and, adjoining thereon, a secondary combustion chamber, in which platen walls are suspended as superheaters. Deposits can form at the lower edge of this superheater. These deposits have to be removed by way of soot blowers. These soot blowers are provided as fixed-wall soot blowers, of which the outlet openings extend, at the height of the lower edge of the superheaters, through the tube wall of the secondary combustion chamber.
Reaction gases resulting from a gasification of solid or liquid carbon-containing energy carriers, in particular of coal, as well as residues of production processes (for example petroleum coke), contain constituents, which act very corrosively on the conventional boiler tube steels. The corrosive effect of such constituents increases with increasing pressure on the gas side and with increasing temperature of the tube wall. The heating surfaces, which are arranged as superheaters, or as evaporators at high vapor pressures or as economizers at end temperatures above 280.degree. C., are particularly attacked. The application of high value Chrome/Nickel steels or Chrome/Nickel alloys makes such coolers much more expensive, without reliably solving the problem. Furthermore, in many cases the susceptibility of these materials is increased, as compared to an unintended dropping below the dew point coupled with most acid reacting fuel ashes and/or relative to chloride corrosion.
On the other hand, in the case of increased gas side pressures, the heating surfaces have to be located in a pressure vessel, whereby the accessibility of the heating surfaces is made more difficult. In order to keep the dimensions of the pressure vessel as small as possible and to avoid having moving parts within the pressure vessel, the soot blowers required for cleaning the heating surfaces in the gasification of coal must be provided as fixed soot blowers, whereby in the known constructions the accessibility is further made more difficult.